The present invention relates to absorbent articles for retaining body fluids such as urine, menses, or faecal material, and in particular to their ability to acquire and retain aqueous based materials. The invention further relates to disposable absorbent articles such as baby diapers or training pants, adult incontinence products, and feminine hygiene products.
Disposable absorbent articles are well know from the art for receiving and retaining bodily discharges, such as urine, menstrual fluids, or faecal materials. Thereby, two basic mechanisms are relied on. First, the containment of such discharges is generally achieved by a gasketing functionality, such as through impermeable materials or construction of sealings between the article andxe2x80x94in most casesxe2x80x94the skin of the wearer. The other key mechanism is to retain the discharges within the absorbent article, generally achieved by using an absorbent structure to pick up the discharges. In most cases, the absorption mechanism is directed towards handling of the aqueous components of the discharges.
One of the key performance criteria against which a absorbent article has to deliver is the acquisition speed. Obviously, a fast liquid acquisition warrants a short time span between exudation and storage of the exudate. Another key performance criterion is the dryness of the user facing surface of the absorbent article. To match the wearing comfort of regular underwear, a dry touch of the user facing surface is desired.
Thereby, one of the key basis transport and storage phenomena is related to the capillary effects of the structures, whereby two properties of the materials used for constructing such structures are of critical importance. First, the porosity of the structure respectively of the materials comprised in that structure. A great number of prior art has been directed against optimising the porosity, or pore size, be this in fibrous structures, or foamed structures, or structures essentially made of particulate materials, or combinations thereof.
Second, the surface tension effects. Also here, a great number of prior art has been dealing with the surface energy of the materials used in such structures. Thereby it is generally accepted, that the xe2x80x9cultimate storage materialsxe2x80x9d have to be relatively hydrophilic, whereas the xe2x80x9cinitial acquisitionxe2x80x9d materials can be less hydrophilic to allow better rewetting properties. This, however, has to be balanced with pore size requirements to still allow rapid fluid pick up into the article. It has also been recognised in the prior art, that these properties have to be considered not only for the first wetting instance, but that also subsequent loadings have to be taken in consideration.
As a consequence, a number of prior art deals with creating xe2x80x9cgradient structuresxe2x80x9d have been disclosed, wherebyxe2x80x94in direction of the fluid flowing into the absorbent structurexe2x80x94the materials exhibit different degrees of hydrophilicityxe2x80x94optionally in combination with other parameter impacting on the capillary transport properties, such as porosity or pore size. This aims at allowing easy penetration of the fluid into the article whilst reducing the ability for rewetting.
The hydrophilicity requirement was readily fulfilled for natural fibre based structures, such as cellulose of fluff based structures. Also, xe2x80x9csemi-syntheticxe2x80x9d materials like viscose/rayon maintained a intrinsic hydrophilicity throughout the material making process until the use in such structures. Further, a certain family of synthetic materials exhibit a natural hydrophilicity like polyester-based materials or polyacrylate materials. However, a number of materials being otherwise suitable for applications in such structures were hydrophobic by nature, for example polyolefinic resins, such as polyethylene or polypropylene from which webs to be used as topsheet could be made.
Consequently, a significant effort was spent against rendering such materials sufficiently hydrophilic at least on their surface so as to allow good wettability. One approach is to apply surfactants to the surface only, and often these were readily removable from this surface. This was thought to be beneficial for rewetting properties, however, for subsequent loadings the surface was left hydrophobic, with the risk of poor performance such as leakage.
Such structures and materials are for example disclosed in EP-A-0.469.591 (Hamajima); EP-A-0.312.118 (Meyer); EP-A-0.670.154 (Everett); EP-A-0.257.280 (Luceri); EP-A-0.359.501 (Cadieux); WO 91/14414 (Newkirk); U.S. Pat. No. 3,614,055 (Mesek); U.S. Pat. No. 4,077,410 (Butterworth);
Attempts to bind specific surfactants more strongly to the surface are described in EP-A-0.598.204 (Garavaglia) or WO 95/10648 (Everhardt).
One further approach in the prior art attempting to address this issue was to incorporate surfactants into the resins of such polymers, and/or by xe2x80x9cattachingxe2x80x9d the surfactants more firmly to the surface to maintain the hydrophilicity over subsequent loadings, such as described in EP-0.340.763 (Hansen).
In WO 96/28602 (Quincy), wettable materials such as films or fibrous webs are described, with a hydrophobic surface having coating which includes a surface free energy modifier, such as a protein, and a surface-active agent, such as a polyethoxylated alkylphenol. Such materials aim at optimising the wettability and penetration of porous materials by fluids wetting such films or fibrous webs.
However, none of the aforementioned prior art documents provided an absorbent article that features a permanently hydrophobic topsheet and still exhibits fast liquid acquisition and a low rewet. In this context, it is to be noted that topsheets comprising a skin care composition have become very popular recently such as for example those taught in WO 96/16682 (Roe et al.). The user facing surface of these topsheets isxe2x80x94due to the hydrophobic nature of the skin care compositionsxe2x80x94at least partially hydrophobic over the entire usage period.
To further improve the liquid handling properties of absorbent article comprising such hydrophobic topsheets, it has been taught in PCT/US97/20842 (Roe) to use an apertured carrier covered with skin care composition as the topsheet allowing to cover the entire area in between the apertures with a skin care composition.
Independent of the above liquid handling aspects, it has been another recent trend in the absorbent article field to provide absorbent articles with apertured topsheets over open structures in order to be able to acquire and store faecal materials such as for example those described in WO 95/05139 (Roe). Such open structures have large open pores to store faecal material. On the other hand, such large open pores limit the liquid handling capabilities of such open structures by reducing their capillary suction. More specifically, such open structures are less efficient in acquiring liquid from a overlying topsheet thereby drying out that topsheet.
It is an object of the present invention to provide an absorbent article which overcomes the problems posed by the prior art absorbent articles.
It is a further object of the present invention to provide an absorbent article with improved liquid handling performance having an fibrous, apertured topsheet.
It is a further object of the present invention to provide an absorbent article with improved liquid handling having a hydrophobic topsheet.
It is a further object of the present invention to provide an absorbent article with improved liquid handling having a low retention liquid in the topsheet.
It is a further object of the present invention to provide an absorbent article with improved liquid handling having a topsheet comprising a skin care composition.
It is a further object of the present invention to provide an absorbent article having a structure having large open pores under an apertured topsheet.
The present invention provides a disposable absorbent article having a transverse centerline, a first region, and a second region, said front region being positioned forward of said transverse centerline, said front region coming into contact with the front waist of the wearer during use, said back region being positioned backward of said transverse centerline, said back region coming into contact with the back waist of the wearer during use. Said disposable absorbent article comprises a liquid pervious, fibrous, structured carrier, a liquid impervious backsheet at least partially peripherally joined to said structured carrier, a liquid storage structure positioned intermediate said topsheet and said backsheet, and a liquid handling structure positioned intermediate said topsheet and said liquid storage structure. A portion of said liquid handling structure is positioned in said first region, a portion of said liquid handling structure is positioned in said second region. The disposable absorbent article of the present invention is characterised in that said structured carrier has a liquid retention of less than less than 150 mg for a test liquid having a surface tension of 33 mN/m, and said liquid handling structure has a basis weight to uncompressed calliper ratio of less than 100 grams per square meter per millimeter.
The present invention further provides a disposable absorbent article wherein said structured carrier is oleophobic has a liquid retention of less than less than 50 mg for a test liquid having a surface tension of 62 mN/m.
The present invention further provides a disposable absorbent article disposable absorbent article has a front region total product acquisition performance of more than 3.75 ml/s in the first gush and of more than 0.5 ml/s in the fourth gush.
The present invention further provides a disposable absorbent article wherein said disposable absorbent article has a front region Skin Hydration rewet value of less than 120 milligrams.
The present invention further provides a disposable absorbent article wherein said structured carrier has a contact angle with distilled water of more than 90xc2x0.
The present invention further provides a disposable absorbent article wherein said liquid handling structure has a compression resistance of at least 70% under an applied pressure of 1 Newton per square centimeter.
The present invention further provides a disposable absorbent article, wherein at least a part of that surface of said structured carrier which faces the wearer during use comprises a surface finish selected from the group of fluoropolymers, chlorofluoropolymers, silicone coating.
The present invention further provides a disposable absorbent article wherein said structured carrier comprises a plurality of apertures having a size of at least 0.2 mm2.
The present invention further provides a disposable absorbent article wherein said structured carrier has a open area of more than 12%.
The present invention further provides a disposable absorbent article wherein said structured carrier comprises is a layer of nonwoven material.
The present invention further provides a disposable absorbent article wherein said structured carrier comprises a skin care composition which is at least partially transferable to the skin of the wearer during use.